The present invention relates generally as indicated to an expansion/check valve assembly including a reverse flow rate adjustment device and more particularly to a valve assembly that allows the flow rate of a fluid flowing reversely through an open check valve port to be selectively adjusted.
One type of typical refrigeration system includes a compressor, a condenser, a receiver, and an evaporator. The compressor receives refrigerant vapor at a relatively low pressure and delivers it to the condenser at a relatively high pressure. The condenser liquefies the refrigerant and delivers it to the evaporator by way of the receiver. At the evaporator, the fluid evaporates and absorbs heat from the external surroundings thereby cooling the relevant environment. The evaporated refrigerant fluid is then delivered (via a suction line) to the compressor to complete the conventional refrigeration cycle.
An expansion or control valve is typically provided upstream of the inlet to the evaporator. This valve controls the flow of high pressure liquid refrigerant from the receiver and provides that it is delivered to the evaporator at a relatively low pressure. One type of expansion valve includes a metering valve member movable within the valve body to selectively open and close an expansion port in response to temperature and pressure changes in the refrigerant fluid discharged from the evaporator.
A large scale refrigeration system, such as for use in, for example, a supermarket setting, may include a plurality of evaporators. The evaporators are commonly arranged in a parallel relationship and an expansion valve is located at the inlet of each individual evaporator. During the cooling cycle, high pressure liquid refrigerant is provided to each of the evaporators from a common supply line and the evaporated refrigerant is returned to the compressor via a common suction line.
As indicated above, the function of the evaporator is to absorb heat from the relevant environment whereby it is commonly constructed of coils to maximize heat transfer area. If the evaporator""s coils become covered with frost and/or ice, this reduces the heat transfer area thereby impairing the system""s efficiency. For this reason, most refrigeration systems include the ability to initiate a defrosting cycle wherein the coils are temporarily xe2x80x9cwarmedxe2x80x9d to remove the ice and frost therefrom.
One common defrosting method is to pass xe2x80x9cwarmxe2x80x9d refrigerant fluid reversely through the evaporator coils. Specifically, refrigerant vapor from the discharge of the compressor is introduced to the outlet of the evaporator, passes reversely through the coils, exits the inlet of the evaporator, and returns to the compressor suction. In a large scale refrigeration system with parallel evaporators, the warm vapor from the compressor""s discharge is introduced to the outlet of each of the individual evaporators through a common supply line.
During the defrosting cycle, the reversely flowing refrigerant fluid circumvents or bypasses the expansion valve. To this end, a bypass line may be provided, this bypass line including a check valve to insure that fluid circumvents the expansion valve only during the defrost mode. Such bypass lines usually require a significant amount of extra plumbing, especially in a large scale refrigeration system including a plurality of evaporators. Specifically, each separate check valve bypass line requires the installation of two tees, one on each side of the expansion device. This extra plumbing, and/or the multiple joints inherent in this plumbing, adds additional installation expenses, increases the possibility for leaks, and complicates infield service checks.
To eliminate the need for separate check valve bypass lines, a combined expansion/check valve assembly may be provided. Such a valve assembly is designed to control the flow during the cooling cycle while at the same time allowing for relatively unrestricted flow during the defrosting cycle. The expansion/check valve assembly typically includes a valve body, an expansion valve device, and a check valve device. The valve body defines a forward flow path through an expansion port and a reverse flow path through a check valve port. The expansion valve device opens and closes the expansion port to control flow rate through the forward flow path. The check valve device closes the check valve port to close the reverse flow path and opens the check valve port to open the reverse flow path.
In a large scale refrigeration system including parallel evaporators, the evaporators are varying distances from the compressor and thus varying distances from the supply of warm defrost gas. Consequently, the evaporators closest to the compressor tend to defrost faster than those farther away thereby causing an xe2x80x9cunbalancedxe2x80x9d defrost situation. This unbalanced defrost situation may result in the evaporators closest to the compressor being excessively warmed (and perhaps threatening the temperature of the product being refrigerated) and/or the evaporators farthest away from the compressor being inadequately defrosted.
If separate check valve bypass lines are used to circumvent the expansion valve, hand valves may be installed on the bypass lines to control the rate of flow therethrough. In this manner, the hand valves on the bypass lines for the evaporator(s) closer to the compressor could be opened a lesser amount than those hand valves on the bypass lines for the evaporator(s) farther away from the compressor. By appropriately setting the hand valves for the individual evaporators, it is possible to xe2x80x9cbalancexe2x80x9d the warm defrost flow to all of the evaporators to more evenly and effectively defrost all of the evaporators. Significantly, the hand valves allow this balancing to be based on the actual defrost characteristics of the refrigeration system after it is up and running. Moreover, the hand valves can be reset when necessary to accommodate changes in the defrost characteristics due to, for example, an uneven load distribution among the different evaporators.
Accordingly, it is possible to xe2x80x9cbalancexe2x80x9d the defrosting of parallel evaporators if separate check valve bypass lines are used. However, as was indicated above, it is usually preferred to eliminate such separate check valve bypass plumbing by using a combined expansion/check valve assembly. While such a valve assembly controls the reverse flow direction of the warm defrost gas, it is not possible to control the rate of this reverse flow. Thus, once the combined expansion/check valve assembly is installed in the refrigeration system, it is not believed to be possible and/or convenient to adjust the defrost flow rate through the different evaporators.
The present invention provides a combined expansion/check valve assembly which allows for adjustment of the flow rate during the reverse flow conditions. Specifically, the valve assembly of the present invention allows a manual adjustment of the reverse flow rate through the check valve. In this manner, it is possible to balance the defrosting of parallel evaporators based on the actual defrost characteristics of the refrigeration system and to refine this balancing when necessary to accommodate changes in the defrost characteristics. Thus, the valve assembly of the present invention provides manual on-line adjustments while still eliminating the need for separate check valve bypass plumbing.
More particularly, the present invention provides a valve assembly comprising a valve body, an expansion valve device, a check valve device and a reverse flow rate adjustment device. The valve body defines a forward flow path through an expansion port and a reverse flow path through a check valve port. The expansion valve device opens and closes the expansion port to control flow rate through the forward flow path. The check valve device closes the check valve port to close the reverse flow path and opens the check valve port to open the reverse flow path.
The reverse flow rate adjustment device controls flow rate through the reverse flow path when the check valve port is opened. Preferably, the adjustment device includes a flow rate control member within the valve body and an adjustment member accessible outside of the valve body. The flow rate control member is operably coupled to the adjustment member and the adjustment member preferably includes a visual indicator viewable outside of the valve body to indicate the position of the control member.
According to one embodiment of the invention, the flow rate control member may control the flow rate by selectively changing the flow area of the check valve port and, if so, is preferably positioned upstream of the check valve port. The flow rate control member preferably comprises a shaft operably coupled to the adjustment member. The shaft has either an inclined distal end surface or a stepped distal end surface that is positioned perpendicularly adjacent the check valve port in the maximum flow position and that is positioned perpendicularly opposite the check valve port in the minimum flow position. Alternatively, the shaft may have a transverse opening that is aligned with the reverse flow path through the check valve port in the maximum flow position and that is positioned perpendicular to the reverse flow path through the check valve port in the minimum flow position.
To move the flow rate member between a maximum flow position and a minimum flow position, the adjustment member is turned in a plane parallel to the reverse flow path through the check valve port. Preferably, the adjustment member is turned less than one full rotation to move the flow rate control member between the maximum flow position and the minimum flow position. Specifically, if the shaft has the inclined or stepped distal end surface, the adjustment member is turned 180xc2x0 and if the shaft has the transverse opening, the adjustment member is turned 90xc2x0.
Instead of a shaft that rotates in a parallel plane, the flow rate control member may comprise a shaft that moves in a direction perpendicular to the reverse flow path through the check valve port. In this case, the adjustment member is turned a plurality of rotations to move the flow rate member between a maximum flow position to a minimum flow position. The shaft may have a flat distal end surface, a tapered distal end surface or a rounded distal end surface, depending on the desired flow patterns.
According to another embodiment of the invention, the flow rate control member controls the flow rate by selectively limiting the movement of a check valve member away from a check valve seat and is preferably positioned downstream of the check valve port. In this embodiment, the adjustment member is turned less than one full rotation (preferably 180xc2x0) to move the flow rate member between a maximum flow position and a minimum flow position. The flow rate control member comprises a shaft having a projection extending from its distal end. The projection holds the check valve member a certain distance away from the check valve seat in the maximum flow position and a lesser distance in the minimum flow position.
The valve assembly of the present invention may be installed in a refrigeration system at the inlet of the evaporator so that the reverse flow rate adjustment device can be adjusted to control flow rate through the reverse flow path and thereby control defrost conditions. Specifically, the refrigerant fluid is passed reversely through the evaporator whereby the check valve port is opened and the adjustment member is manipulated to control the flow rate through the reverse flow path. Also, a plurality of the valve assemblies may be installed in a large scale refrigeration system including a plurality of evaporators (e.g., in a parallel relationship) and the respective reverse flow rate adjustment devices adjusted to balance defrost conditions between the evaporators.
These and other features of the invention are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail certain illustrative embodiments of the invention, these embodiments being indicative of but a few of the various ways in which the principles of the invention may be employed.